Home – Home – Jornals – Atmospheric and Oceanic Optics 2021 number 11

The results of experimental studies of the features of formation and path propagation of high-intensity light channels under conditions of distortions of the initial profile of a high-power femtosecond laser radiation beam are presented. The distortions are introduced by amplitude modulation of the laser beam with the help of masks. The use of amplitude masks allows generation of a preset number of high-intensity light channels and their controllable filamentation mainly at short (tens of meters) distances of radiation propagation in air.

The first experience of using the differential spectroscopy technique DOAS for retrieving the total ozone content (TOC) from measurements of the ground-based UV spectrometer UFOS is considered. Examples of spectra recorded by UFOS and similar spectral equipment are presented. Test calculations of TOC with the use of DOAS are performed based on the UFOS measurements for several days at the Voeikovo station. The resulted TOC values are compared with independent ground-based and satellite measurements. The TOC calculations systematically differ from independent data, which can apparently be eliminated by means of a more accurate adjustment of the DOAS algorithm to the problem conditions and UFOS parameters.

The absorption spectrum of a natural sample of carbon dioxide has been recorded in the 4350-4550 cm^-1 wavenumber range with a Bruker IFS 125HR spectrometer and a 30 m multipass gas cell with a White-type optical system. The spectrum was recorded with a spectral resolution of 0.02 cm^-1 at a pressure of 306 mbar, a temperature of ~ 301.7 K, and a path length of about 1058 m. That, along with 9800 interferograms, allowed attaining a sensitivity of 10^-9 cm^-1. The positions and intensities of 453 spectral lines of 17 bands of 5 carbon dioxide isotopologues (¹²C¹⁶O₂, ¹³C¹⁶O₂, ¹⁶О¹²C¹⁸O, ¹⁶О¹³C¹⁸O, and ¹⁶О¹³C¹⁷O) were measured. The 33303-02201, 41104-02201, and 41104-10002 bands of the principal isotopologue ¹²C¹⁶O₂ and the 31103-00001 band of both ¹³C¹⁶O₂ and ¹⁶О¹²C¹⁸O isotopologues were recorded for the first time. The measured line positions and intensities are compared with the values from the HITRAN2020 database.

The effects of selective and non-selective absorption by atmospheric molecules on the characteristics of radiation scattered by atmospheric aerosol in the presence of organic compounds in the latter are analyzed. The wavelengths at which the backscattered signal exceeds the total absorption are determined.

A simple and convenient form of the vibrational-rotational kinetic energy operator for symmetric molecules of the A₂B₂ type in polyspherical orthogonal coordinates is proposed. A feature of the proposed approach is the symmetry of the kinetic energy operator with respect to the permutation of the coordinates of two groups of atoms (AB) and the ease of applying contraction of wave functions. A variational calculation of the lower vibrational-rotational energy levels of the acetylene molecule has been made. The energy levels calculated in this work are compared with other sources.

The frequency behavior of spectral contributions from initial, central, and “final” sections of the power-law structure function to the spectral density of a stationary random process is considered. Their oscillating alternating-sign frequency character is demonstrated. As the frequency increases, the rate of decrease in the absolute values of these contributions approaches the inversely proportional dependence. Simple analytical approximated relationships describing the frequency behavior of the spectral contributions are suggested and analyzed. They are recommended for wide practical use. The application of the obtained relationships for more complex composite power-law functions is considered.

A change in the air composition during the transition from the troposphere to the stratosphere is investigated on the basis of aircraft sounding data. Distribution of eight gases, dispersion and chemical composition of aerosol is analyzed. It is shown that at the intersection of the tropopause, the concentrations of N₂O, CO, and CH₄ sharply decrease, while of O₃ and NO₂ and the counting concentration of aerosol, on the contrary, increase. In the elemental composition, Si dominates the tropopause; in the ion, SO₄^2-. Terrigenous elements Al, Cu, and Fe are dominated in the troposphere; and among ions, a set of several compounds varies with region. Noticeably different particle dispersions are also identified.

A large-scale comprehensive study of the composition of the troposphere of the Russian Arctic was carried out in September 2020 onboard the TU 134 “Optic” aircraft laboratory. The results of the study of the spatiotemporal variability of aerosol and black carbon (BC) concentrations are considered. The airborne sensing data were used for the analysis of general and particular features of the spatial variability of vertical profiles of aerosol and BC concentrations. The columnar BC concentrations in the arctic and subarctic latitudes were obtained.

Using a new method for determining the parameters of wind turbulence from the spectra of the vertical wind speed measured by a pulsed coherent Doppler lidar (PCDL), an experiment was carried out in 2020 on the coast of Lake Baikal as part of the study of turbulence and internal gravity waves (IGW) in the atmospheric boundary layer (ABL). The article presents the results of this experiment and analyzes the spectra and lidar estimates of the variance of the vertical wind speed and the turbulent energy dissipation rate obtained from the measurements of the Stream Line PCDL in the presence of a low-level jet and IGW in the ABL.

In this work, we examine the transport of combustion aerosol into the stratosphere in summer 2019, when numerous wildfires occurred in Siberia, Canada, and Alaska. According to lidar observations carried out in Tomsk at the stratospheric lidar station of IAO SB RAS in August 2019, distinct layers of aerosol scattering were detected in the lower stratosphere. The analysis of back air mass trajectories calculated on the basis of satellite radiometric information about fires in the Northern Hemisphere and CALIPSO lidar data allows a conclusion that the aerosol layers observed were formed by the combustion products of fires in Siberia transported into the stratosphere.

Different methods for measuring random wavefront tilts are considered. Possibilities of measuring the Fried parameter by the differential method in turbulence sensing and adaptive optics problems are determined. Comparative measurements of the level of turbulence along a horizontal path were carried out by two optical methods: (1) with a differential turbulence meter and (2) a passive method based on image jitter measurements with a high-speed digital video camera mounted at a small astronomical telescope and real-time processing algorithms. Possible differences in the measurement results are discussed. Patterns of the evolution of the convective motion of a medium inside a volume are derived in terms of the velocity field and scalar temperature and pressure fields on the basis of numerical solution of the system of Navier-Stokes equations. Ways of developing a wavefront sensor which ensures high-precision phase measurements in both Kolmogorov and non-Kolmogorov turbulence are suggested.

A method of ultraviolet radiation dosimetry based on recording the photostimulated transition Mn³⁺ + e^– → Мn²⁺ in ultrafine MgO with a periclase crystal structure is described. The observed effect is associated with the photosensitivity of transition metal impurity ions. The intensity of the electron paramagnetic resonance (EPR) signal of Mn²⁺ ions can be used as a measure of change in the valence state of Mn impurity ions in MgO lattice. The possibility of recording a photostimulated transition by the EPR is proposed to be used in the development of a passive integrating ultraviolet detector (UV detector). The applicability of the new UV detector for assessing the ultraviolet transparency of snow cover is shown. The possibility of its use for monitoring the ultraviolet radiation on the Earth's surface in the framework of studies of the stability of tundra ecosystems in the conditions of depletion of the stratospheric ozone layer in the Arctic is discussed.